Rb25 Hi Flow Turbo And Vct Help

[honan]

Hi guys

just wondering if anyone has had this issue:

after blowing the exhaust wheel off the back of my factory turbo, i have now fitted a hi flow factory job.

the housings were both brand new and has a genuine garret 30 71 or 76 core, cant remember now its been a while.

fuel upgrade, rb20 ecu-with nistune,  z32 afm, fmic, 3 inch turbo back and is makin 255rwkw at 16psi.

BUT its coming onto boost ALOT later im talkin maybe 1000-1200rpm later. its not a massive turbo, i had it tuned at morpowa and they weren't sure why it would be doing it either. 

has anyone here experinced the same thing?

also with the rb20 ecu the vct is no longer playing a part, is there something i am supposed to do with the electronics for the vct? ground it or switch it to one position or the other? as far as im aware this hasnt been done? any clues on what to do?

im happy with the power but would love it on a little earlier

help will be much appreciated!

thanks

[luvpsi]

when i was looking at the nistune option i was told i had to make a switch for the vct to turn it on and off. i beleive this has been coverd a few times

here read this thread on nistune

http://www.skylinesaustralia.com/forums/topic/181930-nistune/page__st__320__p__5667436__hl__nistune__fromsearch__1#entry5667436

[raZ1911]

Or get a 300zx ecu and tune it. If you didnt want to mess around with the vct controller.

[PM-R33]

Yep you will need an external RPM switch to control the VCT.

I actually have a NOS RPM Controller for my nitrous system that I don't really need any more because the Vipec can do it now. I know people some times use them so I might sell it if you wanted it.

[badhairdave]

BUT its coming onto boost ALOT later im talkin maybe 1000-1200rpm later. its not a massive turbo, i had it tuned at morpowa and they weren't sure why it would be doing it either.

It's not a massive turbo but it is still significantly larger than the stock one.

A fair chunk of your issue is vct. The window switch mentioned by pm-r33 is the easiest way to get it working properly again.

[R31Nismoid]

also if its a 3076 in factory housing and not Garret proper housing, that's a problem in itself.

[Sunkist]

also if its a 3076 in factory housing and not Garret proper housing, that's a problem in itself.

why is that? If you machine the housings they will fit fine?

or is there some sort of airflow restriction.

[R31Nismoid]

they don't flow enough, and often the wheels are modified, making them less responsive again.

[paulr33]

an rb25 with VCT disabled runs like ass between 1800rpm and 4500rpm

its bascially sluggish and feels like ass

it still runs and will make boost, just sluggish like you said

why did the workshop tune it like this?

in summary as phil said you need a window switch to turn on VCT and turn it off as well

they are called RPM window switches

or get 300zx ECU and retune

[bubba]

an rb25 with VCT disabled runs like ass between 1800rpm and 4500rpm

its bascially sluggish and feels like ass

it still runs and will make boost, just sluggish like you said

why did the workshop tune it like this?

in summary as phil said you need a window switch to turn on VCT and turn it off as well

they are called RPM window switches

or get 300zx ECU and retune

+11ty

The muppets that installed my Haltech changed the water temp sensor to suit, but the factory ECU is still in there controlling VCT/auto/etc. The consequence of changing the water temp sensor is that it has a different resistance to the factory sensor, which causes the stock ECU to read the water temp. about 15-20deg too low (meaning VCT doesn't function until the water temp is up around 95deg, stock ECU needs to see 70deg to enable VCT but normal operating temp as seen by the stock ECU is 60-65deg).

What that means is, with my bigass highflow, it is a laggy POS until 4500rpm. It builds boost from about 3000rpm but doesn't really do anything with it until 4500rpm. When I use Datascan to force the stock ECU to see 70deg, it makes a HUGE difference to the midrange, instead of building boost and doing nothing with it, it actually starts to haul ass a lot earlier than normal. It even makes 4th gear (top in my auto) usable instead of having to drop back to 3rd.

[honan]

mine comes on around 3000rpm and is on fairly well by around 4000rpm but when it comes on it comes on hard as hell.

i was originally going to one tuner and they screwed me big time and i went to morpowa instead.

simon was great, sorted everything out but the vct was an issue never sorted by the guy actually fitting the nistune itself.

i will speak to them tomorrow and get this sorted, hopefully its the issue. i thought this could have something to do with it. any idea on connections with either a vtec controller*shudders* or nitrous window switch, i have no idea about where anything with the vct is?

ive seen alot of cheap controllers on ebay but there all pre programmed and i dont know what rpm to have them set at until its tuned...nitrous switch it is i think!

Edited February 14, 2011 by honan

[honan]

SO after a little research, it seems a nos switch will be the way to do this.

and i fitting it myself shouldnt be a drama(once i know what pin does what on the solenoid)

can the tach signal just be picked up from the ecu?

my car has recently been tuned will it need to be retuned?

also what rpm range should it be set on? i know it should activate the solenoid just after touching the throttle(98%sure) and off at around 4000-4500 rpm, is this right?

when my vct was connected the solenoid was really loud, like a clicking sound, normal or fecked?

Edited February 14, 2011 by honan

[PM-R33]

Yep it is ment to click. Set the VCT up dependent on your car. Run it on the dyno with the VCT completely disengaged and than run it engaged the whole time. Where the two power curves over lap is a good spot to disengage it.

[JonnoHR31]

ecu has a tacho signal wire, tap into that.

pretty sure the vct is switched via the earth and has constant power.

best way to figure out rpm points, as said, is to use a dyno. but if this isnt practical for you, set it to ~1000rpm engage and ~4500rpm disengage.

as for the tune, fuel should be fine but timing might need a bit of tweaking.

[honan]

yeah ill wire it in and leave it, take it to a dyno not far from here, he can run it, ill do the tweaking...hes good at what he does if you have an xr6 turb, then ill head down to adel soon and get the timing and tuned touched up a little to suit.

thanks guys help is extremely appreciated, it may take a little while but ill keep ya posted.

pullin 260rwkw is fun but with better response its going to be an animal compared to what it is now.

[KiwiRS4T]

You may be able to shift the power band a little with an adjustable exhaust cam gear (as well as first enabling vct).

[honan]

yeah i have considered this, i see greddy also do an adjustable gear for the intake side aswell. but the exhaust side should be fine.

ill speak to the guy who tuned it sometime today and also organise a bit of time on a dyno also. once the vct is set up ill consider everything else!

[honan]

i have spoken to one of the guys that tuned the nistune and he says that in the end it is personal preference and that the rpm switch is one option to look at.

he says he doesn't personally use the vct, and that using can either do 2 things..make a big difference in response, or make f**k all difference in response.

I think any improvement is better than none and for the price of an rpm window switch and $190 to have the tune touched up that its worth trying out.

[bubba]

20 degrees of advance on the intake cam makes a huge difference to the midrange.. if you were in Perth I could show you just how much of a difference, VERY noticable.

Edited February 15, 2011 by bubba

[badhairdave]

Shit, my SR20DE makes an extra 10-15rwkw through the midrange with VCT on. If your tuner isn't seeing gains then he's doing something wrong.